A nonstop blower in your HVAC system is hard to ignore. First of all, it’s the sound of potentially higher monthly operating costs as the blower consumes significant electricity. Second, a nonstop blower may signify some sort of malfunction in the system.
In normal operation, the system blower should cycle on and off with the furnace. When heating is required to maintain the thermostat temperature setting, the thermostat activates the furnace and the blower. Once the desired temperature is reached, the thermostat turns off the unit and the blower. If the blower continues to run nonstop — even when the furnace cycles off — there may be a problem.
Here are some things to investigate first, as well as when to call for professional service to fix a nonstop blower.
Check the Thermostat
The blower fan setting on the thermostat may be set to “On” instead of “Auto.” In the “On” mode, the fan will run continuously at all times. In “Auto” mode (the normal setting), the blower cycles on and off with the furnace or air conditioner.
Also, if the temperature setting on the thermostat is excessively high, the furnace and blower may run continuously and never reach the temperature setting. Eventually, the furnace can overheat and a safety sensor may shut down the system.
The Next Step
The furnace’s limit switch controls the system blower fan, activating the fan only when the internal furnace temperature is correct. After the air temperature in rooms matches the thermostat setting and the thermostat signals the furnace to shut down, the limit switch keeps the blower running for a short interval to cool down furnace components. Improper setting of the limit switch — or a defective switch — may cause the blower to run nonstop.
For safety as well as accurate diagnosis and repair, troubleshooting the limit switch should be performed by a certified HVAC technician only.
For professional service to resolve a nonstop blower issue, contact Ace Hardware Home Services.
